Photosensitive element containing a photosensitive crystalline polyacetylenic compound and a photoconductive inorganic metal salt

ABSTRACT

The sensitivity of radiation-sensitive polyyne compounds may be extended to longer wavelengths by the incorporation of inorganic salt sensitizers, such as titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulfide.

United States Patent [191 Luckey et al.

[451 Nov. 13, 1973 PHOTOSENSITIVE ELEMENT CONTAINING A PHOTOSENSITIVE CRYSTALLINE POLYACETYLENIC COMPOUND AND A PHOTOCONDUCTIVE INORGANIC METAL SALT [75] Inventors: George W. Luckey; Charles D.

DeBoer, both of Rochester, N .Y.

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22] Filed: Feb. 4, 1972 [21] Appl. No.: 223,773

[52] US. Cl 96/88, 96/l.5, 96/l.8 [51] Int. Cl G03c 1/00 [58] Field of Search 96/88, 1.5, 1.6,

[56] References Cited UNITED STATES PATENTS 3,501,308 3/1970 Adelman 96/88 3,684,509 8/1972 Van den Henvel et al 96/88 3,501,302 3/1970 Foltz 96/48 Primary Examiner-Norman G. Torchin Assistant ExaminerWon H. Louie, Jr. AttorneyRobert W. Hampton et al.

21 Claims, No Drawings PHOTOSENSITIVE ELEMENT CONTAINING A PHOTOSENSITIVE CRYSTALLINE POLYACETYLENIC COMPOUND AND A PHOTOCONDUCTIVE INORGANIC METAL SALT BACKGROUND OF THE INVENTION 1. Field of the Invention In general, this application relates to radiant-energy sensitive compositions comprising crystalline polyacetylenic compounds suitable for image-recording purposes. More particularly, this invention concerns enhancing the sensitivity of such radiant energy sensitive compositions through the utilization of particular sensitizing materials, and includes the enhanced radiationsensitive compositions and the technique of preparation.

it has now been discovered that the sensitivity of polyacetylenic compounds to radiation within the visible region may be substantially increased by the presence of an inorganic salt sensitizer. By utilizing such a sensitizer, as hereinafter described, it is possible to obtain polyacetylenic compositions, and elements comprising such compositions, which are sensitive to radiation in the visible region of the electromagnetic spectrum.

2. Description of the Prior Art Numerous polyacetylenic compositions of matter are reported in the literature along with observations that some undergo color change upon exposure to light and- /or ultraviolet radiation. Included among investigators reporting on polyyne compositions are: Arthur Seher; Ferdinand Bohlmann and his coauthors; and E. R. H. Jones and M. C. Whiting and their coauthors. The radiation-sensitive polyacetylenic compounds taught in the 'art typically contain a minimum of two acetylenic linkages as a conjugated system (i.e., -C E CC 1! C), and with only a few exceptions, carbon atoms in alpha positions to the acetylenic carbon atoms, i.e., those carbon atoms directly connecting to the acetylenic carbon atoms are bonded directly only to carbon and/or hydrogen atoms. These radiation-sensitive polyacetylenic compositions of matter encompass diynes, triynes, tetraynes, higher polyynes and numerous derivatives and related compounds thereof of various chemical classes ranging from hydrocarbon compounds to acids, esters, and diols, to still other compounds of other chemical classifications containing numerous and varied organic radicals.

As is apparent from publications of the aforementioned investigators, methods are known in the art for the preparation of polyacetylenic compositions. Methods also are taught in U.S. Pat. Nos. 2,816,149; 2,941,014, 3,065,283; etc. General preparative methods include: oxidative coupling or oxidative dehydrocondensation reactions of numerous terminal acetylenic compounds to prepare, as desired, symmetrical and unsymmetrical polyyne compounds; dehydrohalogenation reactions to provide compounds containing acetylenic bonds; and variations, modifications and combinations of such two reactions to provide preparative routes for a multitude of polyacetylenic compositions of matter.

From the preceding description of the art and the sources therein mentioned, there are apparent numerous polyyne compounds which may be suitable for use in this invention. For some there is a brief mention of radiation sensitivity, generally in the ultraviolet range, while for others nothing is reported as to radiation sensitivity. However, it is within the skill of the art to readily evaluate a polyynes sensitivity to any given radiation where the same is unknown. Thus, one needs merely to expose samples of a prepared crystalline polyacetylenic composition of matter to various forms of radiant energy and upon exposure to observe whether a visible color change occurs in the exposed composition. If a visible color change occurs upon exposure to a form of radiant energy, then the crystalline polyacetylenic composition of matter is deemed sensitive, for purposes of the present invention, to that specific form of radiant energy.

Radiant energy, as used herein, is intended to include numerous variant forms of radiant energy, encompassing not only the ultraviolet and visible regions (i.e., actinic radiation) and infrared region of the electromagnetic spectrum, but also electron beams, such as developed by cathode ray guns, gamma-rays, x-rays, betarays, electrical corona discharge, and other forms of corpuscular and/or wave-like energy generally deemed to be radiant energy. The various individual crystalline polyacetylenic compositions of concern generally are not responsive to all such forms of radiant energy, but selectively respond to at least one or more of several variant forms thereof. Within the numerous and varied useful crystalline polyacetylenic compositions of matter, some respond rapidly and selectively to certain radiant energy forms, and slowly or not at all to other forms of radiant energy. Most frequently, response to a particular form of radiant energy is greatest, and most rapid, at particular narrow regions and wavelengths of the electromagnetic spectrum. Generally, the preferred polyacetylenic compositions are most sensitive to radiation within the ultraviolet region.

Depending on particular requirements for a desired application, such as temperature of use, radiant energy form employed, desired speed of response, desired color of image, and the like, there is presently available a wide selection of useful radiation-sensitive crystalline polyacetylenic compositions of matter for use in imagerecording applications. However, as previously noted, polyacetylenic compositions have in the past been highly sensitive to ultraviolet radiation, and less sensitive to radiation of other wavelengths. Although some of the polyynes comprising the materials described in the prior art are inherently radiation-sensitive, their degree of sensitivity is usually low, and greatest sensitivity usually occurs in the short wavelength portion of the spectrum, so that it is desirable to add materials to increase sensitivity and to shift sensitivity toward the desired longer wavelength portion of the spectrum. Increasing the sensitivity of such systems in the visible region of the spectrum has several advantages: it makes available inexpensive and convenient light sources, such as incandescent lamps; it reduces exposure time; and it allows projection printing through various optical systems.

It is, therefore, an object of our invention to provide a novel class of sensitizers for radiation-sensitive systems which produces an unusual increase in sensitivity and extends the range of sensitivity into the visible wavelengths of the spectrum.

Another object is to provide a novel class of sensitizers for crystalline polyacetylenic compositions.

it is another object to provide useful sensitized compositions comprising a radiatiomsensitive crystalline polyacetylenic compound and an inorganic salt sensitizer.

A further object is to provide processes for the preparation of sensitized compositions, for employment of the same in image-recording applications, and for processing exposed sensitized compositions in various applications.

SUMMARY OF THE INVENTION These and other objects are obtained by the practice of this invention, which invention resides in the use of radiation-sensitive compositions comprising a crystalline polyacetylenic compound and an inorganic salt sensitizer.

The inorganic salt sensitizers of this invention are those generally known as photoconductors, and are metal-containing photoconductors, preferably with energy band gaps greater than about 2.5 electron volts, such as compounds of a metal and a non-metallic element of group VI A of the Periodic Table, (as set out in Langes Handbook of Chemistry). Exemplary are the oxides, such as zinc oxide, titanium dioxide, cerous oxide, columbium pentoxide, tantalum pentoxide, bismuth trioxide; metal sulfides such as cadmium sulfide and zinc sulfide; metal oxychlorides such as bismuth oxychloride; and metal halides such as lead bromide, lead chloride, and thallous bromide, other than silver halides. Metal oxides are especially preferred photoconductors of this group. Titanium dioxide is a preferred metal oxide. Preferred members of this group include titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulfide.

In general, photoconductive inorganic salts have been found to be useful sensitizers. However, it should be noted that each does not necessarily provide the same enhancement of sensitivity. This is particularly true in regards to different classification or classes of polyacetylenic compounds. Whereas certain sensitize rs may provide relatively little enhancement of the photosensitivity of an alkali metal salt of a polyacetylenic dioic acid, the same material may provide a large enhancement of the sensitivity of an alkylamide derivative of polyacetylenic polyoic acid. Similarly, other salts may have little effect upon alkylamide derivatives of polyacetylenic compounds, but may greatly enhance the sensitivity of polyacetylenic amine salts, or urethane derivatives of diyne diols.

The enhancement provided by the salt employed as a sensitizer for the polyyne compound is evidenced by the sensitized composition being able to undergo a significant color change upon exposure to a wavelength of radiant energy other than that to which it was principally sensitive in its unsensitized form, or to undergo said color change at a significantly lower level of radiation intensity. For example, a polyyne compound particularly sensitive to ultraviolet radiation of 2537 A. may possess little or no significant sensitivity to normal daylight. Often this providing of significant daylight sensitivity is accomplished by little or no appreciable loss of the polyynes initial ultraviolet sensitivity. The enhancement provided by the sensitizer is accomplished by a deeper color change and/or faster speed of response of the sensitized composition to the radiant energy inducing the color change.

The sensitized compositions of this invention are prepared by comingling with each other a radiationsensitive polyacetylenic compound and an organornetallic compound, such as previously described. This comingling should provide intimate contact between at least some of the employed polyacetylenic compound and the sensitizer.

A number of suitable polyacetylenic compositions of matter for utilization in the process and elements of this invention are disclosed in US. Pat. No. 3,501,302. The polyacetylenic compositions described therein include photosensitive crystalline acid derivatives, and in particular, certain esters and salts of dicarboxylicterminated polyacetylenic compounds having the structural formula HOOC (CH ),,,l(-C C),,(-Cl-l ),,,2COOH, wherein n is an integer of at least 2 and m and m are integers, not necessarily the same but preferably the same, greater than 5 and less than 10. The preferred photosensitive crystalline acid derivatives disclosed by said patents include: the monoand diesters of these diacids, with particular preference for the lower alkyl esters, and most specifically the alkyl ester derivatives wherein the alkyl-ester moiety contains less than 3 carbon atoms; and alkali metal salts and acid derivatives of these diacids and their half-esters, particularly the potassium salt of the methyl half'ester of the preferred symmetrical diacetylenic diacids. Particularly preferred is the monomethyl ester of l0,l2-docosadiynedioic acid.

Further polyacetylenic compositions which are suitable for utilization according to this invention include alkylamide derivatives such as those which have the structural formula A(Cl-l --(C E C),,(CH ),,--B, wherein: n is an integer greater than I; x and y are each an integer from 0 to 10; A may be a methyl radical, either unsubstituted or substituted, (such as methoxymethyl or ethoxymethyl), COOR, CONHR, CONl-lNl-IR" or CONI-ICONHR", and B is a radical selected from the group consisting of CONHR', CONHNI-IR, and CONl-ICONHR", wherein R may be H or an alkyl of less than 8 carbon atoms (e.g., methyl, propyl, pentyl, octyl, etc. R is an alkyl having from 2 to 12 carbon atoms, (e.g., propyl, butyl, octyl, decyl, undecyl, etc. including substituted alkyls such as hydroxy, polyhydroxy, amino, substituted amino, alkyl thio, COOR, CONE-IR, or methoxy substituted alkyl, and R" may be phenyl or an alkyl having from 2 to 12 carbon atoms. Preferred alkylamides of this nature include: methyl 2l-[N-(3- carboxypropyl)carbamoyl1-10 ,l 2-heneicosadiyne; methyl 2 l -[N-( 3 -hydroxypropyl)carbamoyl]- 10, l 2- heneicosadiynoate; and methyl 2 l N-( 3 carboxypropyl)carbamoyl1- 10,1 Z-heneicosadiynoate.

Suitable radiation-sensitive crystalline polyacetylenic amine salts may have the structural formula B-r-CH- )-,,(C E C),,+Cl-l +-,,COO'A wherein: n is an integer greater than 1; x and y are each an integer from 0 to 10; A is selected from ammonium and substituted ammonium groups, (e.g., N H R, Nfl-I RR, N HRRR N RRR R B is selected from the group consisting of CH COOA", COOR, CONHR", CONHNl-IR", CONI-ICONHR ROOCNH, and RNHCOO radicals, wherein R, R, R and R may be the same or different, and may be H, alkyl (including hydroxy or methoxy substituted alkyl), or aryl, R may be H or an alkyl of less than 8 carbon atoms (e.g., methyl, propyl, pentyl, octyl, etc.), R is an alkyl of from 2 to 12 carbon atoms (e.g., propyl, butyl, octyl, decyl, undecyl, etc.), including substituted alkyl such as hydroxy, polyhydroxy, amino, substituted amino,

alkyl thio, carboxy, or methoxy substituted alkyl, R may be phenyl or an alkyl having from 2 to 12 carbon atoms, and R is an alkyl, including methoxy or hydroxy substituted alkyls of from 1 to 8 carbon atoms, phenyl, or hydroxy substituted phenyl. Suitable polyacetylenic amine salts include hexylammonium -(N- hexylcarbamoyl)-9,l 1 -eicosadiyne-1 -carboxylate, propylammonium 20-(N-propylcarbamoyl)-9,l 1- eicosadiyne-l-carboxylate, and 3-hydroxypropylammonium 20- N-(3-hydroxypropyl)carbamoyl)-9,l1- eicosadiyne-l-carboxylate.

Additional suitable polyacetylenic compounds include polyacetylenic bis urethanes corresponding to the formula [R-NI-ICOO(CII ),,C E C+ wherein n is an integer of l to 4, and R is selected from the group consisting of alkyl radicals of from 1 to 12 carbon atoms, including substituted alkyl radicals such as hydroxy, polyhydroxy, amino, substituted amino, or methoxy substituted alkyl, phenyl and substituted phenyl radicals (e.g., hydroxy, carboxy, and methoxy phenyl). Suitable members of this class of polyacetylenic compounds include 2,4-hexadiyne-1,6-diol bis (N- hexylurethane), and 2,4-hexadiyne-l,6-diol bis(N- butylurethane).

In the practice of the invention there is employed an image-receptive element comprising a carrier means which serves to fixedly position crystals of the radiation-sensitive crystalline polyacetylenic composition. The carrier means functions to hold individual crystals in fixed position in relation to other crystals so that the element, unexposed and exposed, can be handled and moved without displacement and change in position of crystals with respect to each other.

This is not to imply that binderless films are not possible employing polyacetylenic compounds as a photosensitive medium. It is possible to prepare vacuum deposited layers of crystalline polyacetylenic compound. When such compounds are deposited upon a suitable substrate, it is possible to codeposit thereupon a sensitizing amount of a photoconductive inorganic salt sensitizer such as herein described. This codeposition may be accomplished by simultaneously vapor depositing said photoconductive metal salt upon a substrate with the crystalline polyacetylenic compound, or by a separate and distinct vacuum deposition step. Further, it is possible to prepare a vacuum deposited layer of polyacetylenic compound upon a substrate, which layer may then be overcoated with a suitable binder incorporating therein a sensitizing amount of a photoconductive metal salt, in direct contact with said polyacetylenic compound.

The carrier means can be in any of several diverse embodiments. Generally, the carrier means comprise a binder material, such as a natural or synthetic plastic, resin, colloid or gel and the like, wherein the crystals of the photosensitive crystalline polyacetylenic composition of matter are dispersed and held in fixed position. In such instances, the polyyne composition may be mixed as a dope, solution, emulsion, dispersion or the like with the binder material and then processed to provide solid films, sheets, coatings, and the like containing dispersed crystals of the sensitive polyacetylenic composition. Thus, one embodiment of the imagereceptive element is a solid sheet, film, or the like, comprising a binder material as a dispersing medium to position fixedly therein crystals of the radiation-sensitive polyacetylenic composition. Another embodiment of the element is a support material or body to which adheres a film, coating, or the like of the binder material having the dispersed crystals therein. Useful support materials include paper sheet, glass sheet, plastic film, and other conventional and suitable photographic quality support materials. Still an additional embodiment of the element may comprise the support material having adhered thereto a binder-free coating of the crystals of the sensitive polyacetylenic composition of matter. Other element embodiments, as desired, may include a suitable photographic coating material on one or more surfaces and interfaces of the various element embodiments. In addition, other embodiments may comprise polyyne crystals and support means of any of various combinations of the several foregoing components and still other components apparent to those in the art, so long as the carrier means fixedly positions the radiation-sensitive crystalline polyacetylenic composition.

Exemplary support materials include: vitreous materials, such as glass, glazed ceramics, porcelain, etc.; fibrous materials, such as cardboard, fiberboard, paper including bond paper, resin and clay-sized papers, wax or other transparentized paper, paperboard, etc.; cloths and fabrics including those of silk, cotton, viscose rayon, etc.; metals, such as copper, bronze, aluminum, tin, etc.; natural polymers and colloids, such as gelatin and polysaccharides; natural and synthetic waxes, including paraffin, beeswax, carnauba wax, synthetic resins and plastics, including particularly polyethylene, polypropylene, polymers and copolymers of vinylidene and vinylmonomers including polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinyl acetate, vinyl acetate/acrylate, vinyl acetate/methacrylate, vinylidene chloride/acrylonitrile, vinylidene chloride/vinyl acetate, vinylidene chloride/methacrylate, polystyrenes, polyvinyl acetals including polyvinyl butyral, polyvinyl formal, polyvinyl alcohol, polyamides including polyhexamethylene adipamides, N-methoxymethyl polyhexamethylene adipamide, natural and synthetic rubbers including butadiene-acrylonitrile copolymers, 2-chloro-l ,3-butadiene polymers, polyacrylate polymers and copolymers including polymethylmethacrylate, polyethylmethacrylate, polyurethanes, polycarbonates, polyethylene terephthalate, polyethylene terephthalate/isophthalate copolymers and other esters, such as obtained by condensing terephthalic acid and its derivatives with propylene glycol, diethylene glycol, tetramethylene glycol or cyclohexane-l ,4- dimethanol, cellulose ethers including methyl cellulose, ethyl cellulose and benzyl cellulose, cellulose esters and mixed esters including cellulose acetate, triacetate, cellulose propionate, cellulose nitrate and cellulose diacetate; and even nonthermoplastic materials including cellulose, phenolic resins, melamine-formaldehyde resins, alkyd resins, thermosetting acrylic resins, epoxy resins, and numerous other synthetic resins, and plasties as will be apparent to those skilled in the art.

The base or support material may be transparent, translucent, or opaque, and should be selected with due consideration being given to the particular radiant energy to which the employed crystalline polyacetylenic compound is sensitive. It is also selected with due consideration of the intended usage of the imaged element and of the specific radiant energy and technique to be employed in the particular image-recording application. For example, where the imaging technique requires transmission of radiation through the support to expose the polyacetylenic crystals, the support should possess such a transmission characteristic. The base or support may be adhered directly to the radiationsensitive crystals, or indirectly adhered, if desired, by a subbing layer or coating for any of several purposes, e.g., to alter the supports transmission of the radiant energy, to change the supports reflectivity of the radiant energy, to modify adherence to the support or for other reasons. Similar to the support material, such subbing layer is selected with due regard to the specific radiant energy and technique to be employed in the particular image-recording application. Subbing layers for various photographic purposes and methods of coating supports with the same are well known.

Generally and preferably the element is a flat film, sheet, plate or the like, so as to present a flat surface upon which the radiant energy may be directed. However, curved-surfaced and other than flat-surfaced elements, although generally of lesser utility, are not excluded.

Exemplary binder materials of utility as components for the carrier means include: natural and synthetic plastic resins, waxes, colloids, gels and the like including gelatins, desirably photographic-grade gelatin, various polysaccharides including dextran, dextrin, hydrophylic cellulose ethers and esters, acetylated starches, natural and synthetic waxes including paraffin, beeswax, polyvinylacetals, polymers of acrylic and methacrylic esters and amines, hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methyacrylic esters and styrene, vinyl acetate polymers and copolymers and their derivatives, including completely and partially hydrolyzed products thereof, polyvinyl acetate, polyvinyl alcohol, polyethylene oxide polymers, polyvinylpyrrolidone, polyvinyl acetals including polyvinyl acetaldehyde acetal, polyvinyl butyraldehyde acetal, polyvinyl sodium-o-sulfobenzaldehyde acetal, polyvinyl formaldehyde acetal, and numerous other known photographic binder materials including a substantial number of aforelisted useful plastic and resinous support materials which are capable of being placed in the form of a dope, solution, dispersion, gel, or the like for incorporation therein of the radiationsensitive polyacetylenic composition and are then capable of processing to a solid form containing dispersed crystals of the polyacetylenic composition. As is well known in the art, in the preparation of smooth uniform continuous coatings of binder materials, there may be employed therewith small amounts of conventional coating aids as viscosity controlling agents, leveling agents, dispersing agents, and the like. The particular binder material employed is selected with due regard to the specific radiant energy and technique to be employed in the particular image-recording application and invariably is a binder material permitting substantial transmission of that specific radiant energy to be employed. Desirably, the binder material is a nonsolvent, or possesses only limited solvating properties for the polyyne so that the polyyne is capable of existence in its radiation-sensitive crystalline form therein.

Well-known sources, optical systems, camera arrangements, focusing and projection systems and the like for the desired radiant energy are used in employing the image-receptive element in the varied imageforming applications. The resultant images are directly formed print-out images in that they can be seen by the human eye to be a distinctly different color than unirradiated crystals of the element.

The photosensitive image-receptive element may be used in image-forming systems based on transmissionexposure techniques and reflex-exposure techniques. Thus, stencils of a material substantially nontransmissive of the radiant energy may be laid on the imageforming element with the cut-out portion of the stencil allowing the applied radiant energy to strike the element according to the desired image or images. lf desired, the stencil need not contact the element with the radiant energy being projected to pass through the cutout portion of the stencil to strike the element. The element also can be expected by contact or projection techniques through a two-tone image or process transparency, i.e., a process negative or positive (i.e., an image-bearing transparency consisting of areas transmissive and opaque to the radiant energy such as of a socalled line or halftone negative or positive-type transparency) or a continuous tone negative or positive. Likewise an object, whose image is to be obtained, may be placed between the radiant energy source and the element and the radiant energy striking the element will be of an image pattern dependent on the radiant energy absorption and transmission characteristics of the particular object. Reflex-exposure techniques are applicable. For example, by ultraviolet reflecting optic techniques, ultraviolet sensitive image-receptive elements may be used to make photocopies of printed or typed copy. Reflex-exposure techniques are particularly useful for making office copies from materials having messages on both sides of a page, for making images of specimens and objects, and for reproducing messages and the like found on materials not having radiant energy transmissive properties conductive to transmission-exposure techniques.

Where the imaged elements are to be retained for lengthy periods, desirably they are stored, as in an envelope or opaque container, in a manner excluding any stray irradiation of radiant energy of a form affecting the element. This may also be effectively accomplished by overcoating the imaged element with a layer of material which absorbs radiation to which the element is sensitive. Thus, an ultraviolet absorbing layer may be coated over the imaged element. Alternatively, the initially imaged elements may be fixed or converted to a more stable imaged state. In fixing, the unexposed crystalline polyyne is placed in a form in which it is no longer substantially radiation-sensitive, as by solvating it in the binder, changing it from crystalline to liquid state, or washing it out from the element, and the like. In conversion, the initial irradiation induced color is often transformed to another distinctly different color, which is relatively stable to exposure to the initial form of radiant energy inducing the image formation.

A particularly convenient manner to effect a color transformation of the initially induced image is to carefully heat the imaged element to an appropriate elevated temperature, generally between 520C less than the melting point of the nonirradiated crystalline polyyne, at which temperature the initial radiant energy induced color-transformed crystals and crystal portions may transform to a distinctly different color. Temperatures approximating and higher than the melting point of the unirradiated crystalline polyyne will often effect a color transformation of the initial radiant-energy induced colored polyyne crystals, but in so doing there may be some loss in sharpness of the image with some blurring and roughing of the image border or periphery. This can be avoided, or at least minimized, if the colored crystal portions and crystals are firmly held at these temperatures so as to avoid being overcoated or dissolved in melted unexposed polyyne.

Another manner for effecting color transformation of the initial image is exposure to a solvent for the unexposed polyyne. An exposure for about 10 to seconds at an elevated temperature from about 5 to 10 lower than employable for heat fixing generally is satisfactory. Methanol, ethanol, toluene, diethyl ether, butyl acetate, carbon tetrachloride, acetone, 2- butoxyethanol, and like solvents are useful. Water vapor and aqueous solutions, such as aqueous hydrochloric acid, are useful with water soluble polyyne derivatives. Other useful solvents also will be apparent.

An advantage of the element having the image thereof in a distinctly different color than the initial radiation-induced color, is that this other color may be more susceptible to providing print-out copies with good contrast when prints, negatives, and the like, of this image are made by conventional silver halide photographic techniques.

As indicated above, image recording elements utilizing radiation sensitive polyynes may be prepared by fixing the crystalline polyyne on a surface. This may be done, for example, by coating a dispersion of the polyyne in a polymer matrix on a suitable support, by coating a solution of the polyyne in a polymer solution and allowing the polyyne to crystallize upon solvent evaporation, by applying a solution of a polyyne to a paper surface and allowing the polyyne to crystallize upon the fibers, by coating a dispersion of a water immiscible polyyne solution in an aqueous binder and allowing evaporation to form polyyne crystals in the binder matrix, or by simply smearing the polyyne crystals on a suitable support.

A particularly advantageous technique for preparing radiation-sensitive elements according to this invention is by the dissolution of radiation sensitive polyyne crystals in one or more substantially water-immiscible organic solvents (i.e., about 0-25 percent soluble in water, by weight) which are then added to an aqueous solution of a hydrophilic binder. The water-immiscible polyyne solution is then dispersed in the aqueous binder solution, which may also contain a suitable surfactant, and mechanically stirred such as by means of a homogenizer or ultrasonic agitator, to form an oilin-water dispersion, substantially devoid of polyyne crystals. This dispersion is then coated on a suitable support, during which coating the water-immiscible solvent evaporates from the coating with concomitant production of extremely fine crystals of the polyyne, uniformly distributed in the coated hydrophilic carrier. The polyyne elements thus formed are highly sensitive to various forms of radiation, are extremely uniform in particle size, and are very stable. It is desirable that the organic solvent employed to dissolve the polyacetylenic compound according to this technique be waterimmiscible, or essentially so. Thus, solvents having solubilities in water of from 0 percent to about 25 percent are suitable. Exemplary organic solvents include cyclohexanone, ethyl acetate, cyclohexane, dichloromethane, dichloroethane, chloroform, pentyl alcohol, hexyl alcohol, 4-methyl-2-pentanone, benzene, toluene and the like, and mixtures thereof. Varying amounts of solvent may be employed, but generally, from 1 to 5 units (by weight) of solvent may be employed for each unit of polyacetylene to be used, with from 2 to 3 times as much solvent as polyyne being the preferred range. If water-miscible solvents are employed, an immmediate precipitation of dissolved polyyne occurs upon mixing of solvent and aqueous binder solutions, resulting in relatively large average grain size, and accordingly, lower stability and control.

The time required for complete dispersion may vary from several seconds to several hours, dependent upon dispersal technique, materials employed, and size of dispersed phase droplets desired. In general, crystals averaging 1 micron in cross section, may be obtained from an emulsion formed by ultrasonically dispersing a polyyne solution in an aqueous binder for l to 2 minutes. It is to be recognized, however, that blending time may be so selected as to achieve the desired results in accordance with the specific materials employed.

Varying amounts of the polyyne and/or binder material may be chosen, dependent upon anticipated use of the elements produced, among other factors. In general, polyyne to hinder ratios (by weight) may range from about 0.1 to about 3.0 or higher. In terms of coating density, sufficient polyyne may be utilized to provide from about 10 to 2,000 mg of polyyne per square foot of coated element. As indicated, the amount of polyyne employed is quite widely variable, and may be varied to suit the desired utilization, binder, and solvent employed.

In preparing the sensitized elements of this invention according to the above technique, the sensitizing material may be separately dispersed in the solvent employed to dissolve the polyacetylenic compound, and added to the aqueous binder solution with the polyacetylenic solution. Alternatively, the sensitizer may be separately dispersed in the aqueous binder solution.

After blending, the polyacetylenic compound is present in the aqueous binder solution in the form of finely divided, discrete globules of dissolved polyacetylene, which are essentially insoluble in the continuous phase. This emulsion is quite stable, and may be stored for considerable lengths of time before utilization without settling, agglomeration, or breaking.

Radiation-sensitive elements may be prepared by coating the thus formed emulsion upon a suitable support and evaporating the dispersed solvent phase. Any suitable coating means may be employed, such as dip coating, air knife coating, curtain coating, flow coating, bar coating, etc. The coating may be chill set, for ease of handling, if so desired, or allowed to dry to a solid continuous phase at room temperature. During the drying stage, the organic solvent volatilizes, causing the precipitation of discrete particles of radiation-sensitive crystalline polyacetylenic compound.

In addition to comingling in a solvent and subsequent crystal formation, other suitable sensitization techniques include fusion of the sensitizer with the polyyne; adsorption of the sensitizer to the surface of the polyyne; and presence of the sensitizer in the matrix surrounding the polyyne crystals.

Since the inorganic salt sensitizers employed are very often used for pigmentation purposes, care must be taken to limit the sensitizer concentration so as to not inhibit or mask the desired color transformation. The amount of sensitizer which may be added to a particular composition to give optimum sensitization can vary widely. The optimum amount will, of course, vary with the polyacetylenic composition employed, as well as with the particular sensitizing compound. in general, beneficial results may be obtained where an appropriate sensitizer is added at a concentration in a range from about 0.1 to 300 percent by weight based on the weight of the polyacetylenic compound employed, and preferably from about 1.0 to 100 percent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is further illustrated by the following examples.

Examples l4 A slurry is prepared comprising 100 milligrams of the monomethyl ester of lO,l2-docosadiynedioic acid, 5Q ml of acetone, and 200 milligrams of each of the following sensitizing materials: zinc oxide, titanium dioxide, cadmium iodide, and cadmium sulfide. Each slurry is coated on filter paper and allowed to dry.

The dry coatings are then exposed to radiation of 3,660 A. Blue images are obtained with coatings that contain zinc oxide and titanium dioxide. Faint but visible images are obtained with cadmium iodide and cadmium sulfide, while no image is observed with a control coating of the diyne which does not contain the sensitizing materials. Exposure for seconds to x-rays from an x-ray tube operating at 70 KVP and MA at a distance of 20 cm, filtered by 0.18 inch of aluminum, produces a blue image with a coating containing zinc oxide. No image is obtained with the control coating.

Additional elements are prepared as in Examples l-4, employing different inorganic salt sensitizers with a variety of polyacetylenic compounds. Additional non-silver inorganic compounds which also sensitize the formation of images with diyne materials includes bismuth oxychloride, lead chloride, lead bromide, thallous bromide, zinc sulfide, cerous oxide, columbium pentoxide, tantalum pentoxide, and bismuth trioxide. In addition, this sensitization effect is noted in elements comprising polyacetylenic compounds such as alkylamides of polyacetylenic polyoic acids (e.g., methyl 2 1-[N-(3-carboxy-propyl) carbamoyl1- 10,1 2- heneicosadiynoate); polyacetylenic amine salts, such as hexylarnmonium 20-(Nhexylcarbomyl)-9,l l eicosadiyne-l carboxylate; and polyacetylenic bisurethanes, such as 2,4-hexadiyne-l ,6-diol bis (N- hexylurethane).

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A composition comprising a radiation-sensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system and a sensitizing amount of a photoconductive inorganic metal salt having an energy band gap greater than 2.5 electron volts.

2. A composition as set forth in claim 1, wherein said polyacetylenic compound is selected from the group consisting of lower alkyl esters of diyne dioic acid, polyacetylenic polyoic acid alkylamides, polyacetylenic amine salts, and diyne diol urethanes.

3. A composition comprising a radiation-sensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system and a sensitizing amount of a photoconductive inorganic metal salt, wherein said photoconductive salt is selected from the group consisting of metal oxides, sulfides, oxychlorides, and non-silver metal halides.

4. A composition as set forth in claim 3, wherein said salt is selected from the group consisting of titanium dioxide, zinc oxide, cadmium iodide, and cadmium sultide.

5. An element comprising a carrier, a radiationsensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive inorganic metal salt having an energy band gap greater than 2.5 electron volts.

6. An element as set forth in claim 5, wherein said carrier comprises a support to which is adhered a binder having said polyacetylenic compound dispersed therein.

7. An element as set forth in claim 6, wherein said binder is gelatin.

8. An element as set forth in claim 5, wherein said salt is titanium dioxide.

9. An element as set forth in claim 5, wherein said salt is zinc oxide.

10. An element as set forth in claim 6, wherein said polyacetylenic compound is selected from the group consisting of lower alkyl esters of diyne dioic acid, polyacetylenic polyoic acid alkylarnides, polyacetylenic amine salts, and diyne diol urethanes.

ll. An element comprising a carrier, 3 radiationsensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive inorganic metal salt selected from the group consisting of metal oxides, sulfides, oxychlorides, and non-silver metal halides.

12. An element as set forth in claim 11, wherein said photoconductive salt has energy band gaps greater than about 2.5 electron volts.

13. An element as set forth in claim 12, wherein said carrier comprises a support to which is adhered a binder having said polyacetylenic compound dispersed therein.

14. An element as set forth in claim 13, wherein said binder is gelatin.

15. An element comprising a support having coated thereon a layer comprising a binder, a radiationsensitive crystalline lower alkyl ester of diyne dioic acid, and a sensitizing amount of a photoconductive inorganic metal salt having an energy band gap greater than 2.5 electron volts.

16. An element as set forth in claim 15, wherein said ester is the monomethyl ester of l0,l2-docosadiyne dioic acid.

17. An element as set forth in claim 16, wherein said salt is titanium dioxide.

18. An element as set forth in claim 16, wherein said salt is zinc oxide.

19. An element comprising a support having coated thereon a layer comprising a binder, a crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive metal salt selected from amine salts, and diyne diol urethanes.

21. An element as set forth in claim 19, wherein said salt is selected from the group consisting of titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulconsisting of lower alkyl esters of diyne dioic acid, polfide.

yacetylenic polyoic acid alkylamides, polyacetylenic 

2. A composition as set forth in claim 1, wherein said polyacetylenic compound is selected from the group consisting of lower alkyl esters of diyne dioic acid, polyacetylenic polyoic acid alkylamides, polyacetylenic amine salts, and diyne diol urethanes.
 3. A composition comprising a radiation-sensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system and a sensitizing amount of a photoconductive inorganic metal salt, wherein said photocOnductive salt is selected from the group consisting of metal oxides, sulfides, oxychlorides, and non-silver metal halides.
 4. A composition as set forth in claim 3, wherein said salt is selected from the group consisting of titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulfide.
 5. An element comprising a carrier, a radiation-sensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive inorganic metal salt having an energy band gap greater than 2.5 electron volts.
 6. An element as set forth in claim 5, wherein said carrier comprises a support to which is adhered a binder having said polyacetylenic compound dispersed therein.
 7. An element as set forth in claim 6, wherein said binder is gelatin.
 8. An element as set forth in claim 5, wherein said salt is titanium dioxide.
 9. An element as set forth in claim 5, wherein said salt is zinc oxide.
 10. An element as set forth in claim 6, wherein said polyacetylenic compound is selected from the group consisting of lower alkyl esters of diyne dioic acid, polyacetylenic polyoic acid alkylamides, polyacetylenic amine salts, and diyne diol urethanes.
 11. An element comprising a carrier, a radiation-sensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive inorganic metal salt selected from the group consisting of metal oxides, sulfides, oxychlorides, and non-silver metal halides.
 12. An element as set forth in claim 11, wherein said photoconductive salt has energy band gaps greater than about 2.5 electron volts.
 13. An element as set forth in claim 12, wherein said carrier comprises a support to which is adhered a binder having said polyacetylenic compound dispersed therein.
 14. An element as set forth in claim 13, wherein said binder is gelatin.
 15. An element comprising a support having coated thereon a layer comprising a binder, a radiation-sensitive crystalline lower alkyl ester of diyne dioic acid, and a sensitizing amount of a photoconductive inorganic metal salt having an energy band gap greater than 2.5 electron volts.
 16. An element as set forth in claim 15, wherein said ester is the monomethyl ester of 10,12-docosadiyne dioic acid.
 17. An element as set forth in claim 16, wherein said salt is titanium dioxide.
 18. An element as set forth in claim 16, wherein said salt is zinc oxide.
 19. An element comprising a support having coated thereon a layer comprising a binder, a crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, and a sensitizing amount of a photoconductive metal salt selected from the group consisting of metal oxides, sulfides, oxychlorides, and non-silver metal halides.
 20. An element as set forth in claim 19, wherein said polyacetylenic compound is selected from the group consisting of lower alkyl esters of diyne dioic acid, polyacetylenic polyoic acid alkylamides, polyacetylenic amine salts, and diyne diol urethanes.
 21. An element as set forth in claim 19, wherein said salt is selected from the group consisting of titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulfide. 